Among the many types of conveyor belts in general use today for carrying diverse products along both straight and horizontally curved paths two types are grid conveyor belts and flat wire conveyor belts. A grid belt is illustrated in U.S. Pat. No. 3,225,898. Such a belt comprises a plurality of spaced transverse rods slidably interconnected by two rows of connecting links disposed along the inner and outer edges of the rods. The connecting links are disposed in a nested relationship relative to one another with slots in the links slidably receiving the rods. Either edge of the belt can suitably collapse when it is necessary for the belt to travel around a horizontal curve.
The second type of belt, a flat wire belt, is illustrated in U.S. Pat. No. Re. 27,690, the entire contents of which are hereby incorporated by reference. In this flat wire belt, the transverse rods are slidably interconnected by transversely disposed flat wire tractive links having a width spanning substantially the entire length of the rods. The tractive links comprise a plurality of longitudinally disposed tractive members secured together by transversely disposed connecting members to form a plurality of U-shaped segments. Longitudinal slots are provided in the tractive members for slidably receiving the rods. As in the case of the grid type belt, the tractive links are arranged in a nested relationship relative to one another to enable the belt to collapse along either edge to traverse horizontal curves. The tractive links in prior art fiat wire belts are generally positioned such that the terminal ends of the inner and outer links trail with respect to the direction of travel of the belt. This orientation is utilized in order to minimize the amount of damage should the belt contact any stationary framework. In addition, reinforcing bar links are often placed along the outer edges of the flat wire belt for bearing the tractive load of the belt as it traverses the curve and thereby preventing fatigue failure of the flat wire links.
Grid and flat wire belts have enjoyed substantial commercial success because of their ability to traverse horizontal curves while still providing an integrated carrying surface capable of supporting a great variety of products. Another desirable feature of such belts is that they can pass freely in vertical curves around relatively small end pulleys. Although certain prior art belts have required a relatively large horizontal turning radius, a small radius conveyor belt, such as that described in U.S. Pat. No. 4,078,655 which is hereby incorporated by reference, overcomes this limitation and further expands the usefulness of flat wire belts in a variety of conveyor installations.
Grid and flat wire type belts have found particular use in spiral conveying systems such as disclosed in U.S. Pat. Nos. 3,348,659; 3,682,295 and 4,078,655. In such systems, the belt travels in a spiral direction, and is driven by a cage-like driving drum that is located within the spiral. The drum includes cage bars which extend generally vertically and frictionally engage the inner edge of the belt. The drive in such system operates in an overdrive condition wherein there is relative motion of the cage bars forward with respect to the inside belt edge. Prior art belts have generally orientated the innermost edge of the belt with its end trailing in the direction of travel. Thus, as the cage bars pass by, the terminal ends can snag on the cage bars and become bent or damage the cage bars. This type of damage occurs most frequently under adverse conditions, such as when the tension in the belt is high. In wider conveyor belts, those generally more than three feet in width, the tractive links tend to compress in the transverse direction under the tension in the belt. As the tractive links compress, the outer links of the conveyor belt become angled further inward, thus making the terminal ends more prone to snagging on the cage bars by pushing them outward into the plane of the cage drum rotation. These terminal ends can be the terminal ends of the conveyor belt itself or of inside reinforcing links. As shown in FIGS. 10(A) and 10(B), the terminal ends either bend upwards or roll over the adjacent bar links. In both cases, damage to the terminal ends prevents the conveyor belt from properly collapsing and expanding when transversing horizontal curves.